Re: [time-nuts] Helium and MEMS oscillators don;t mix well

[Poul-Henning Kamp]

In message 
, Wayne 
Holder writes:

>The curious thing to me is that some iPhones are said not to recover from
>exposure to helium but, as an essentially mechanical device, I can think of
>no reason that the SiT1532 would not recover from exposure to helium after
>the gas had migrated out.

Most likely: Because some piece of MEMS machinery broke of ?




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Re: [time-nuts] Helium and MEMS oscillators don;t mix well

[Poul-Henning Kamp]

In message <04055a33-5f2b-8aff-f9b0-526c9478d...@earthlink.net>, jimlux writes:

>> To get to relevant He levels via the Radon route, we are talking
>> deep unventilated mineshaft kind of concentrations...
>> 
>> Hydrogen is a lot more plausible in my view.
>
>Yeah, but in concentrations typical in the "room", I doubt you'd see the 
>effect.  The experimenters put the phone in a bag full of helium and it 
>took hours.  I would expect the same in hydrogen.

We're talking across each other here, I was referring to the PRS
anecdote from Karl.

I'll absolutely belive that you can screw up certain kinds of MEMS
devices when you dump 90 kg of Helium into a building.

>That's a lot different than a <1% concentration. I assure you, that if 
>there was a helium leak/vent/boil off that made the room concentration 
>1%, the room oxygen sensor would be alarming (having dropped to 20%) and 
>people would be running for the doors.

That's not my experience, most ${GAS}-level detectors are based on
some kind of chemical reactivty (or spectroscopy if they are _really_
expensive) and they tend to just ignore helium and other noble gasses.

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Re: [time-nuts] Helium and MEMS oscillators don;t mix well

[Bob kb8tq]

Hi

As much fun as this is, once it moves over to wireless charging as the likely 
issue ….. that’s getting pretty far from TimeNuts main focus…..

Bob

> On Nov 1, 2018, at 5:08 PM, David Witten  wrote:
> 
> Ok, one last try:
> 
> From AuntMinnie.com, free but subscrip[tion-based newslettter for clinical
> radiologists and related staff:
> 
> 
> November 1, 2018 -- A second imaging facility is reporting problems with
> Apple devices that appear to be related to the operation of the center's
> MRI scanner. Nearly 10 late-model Apple iPhones and Watches were
> permanently disabled at a Delaware center after it ramped down its MRI
> magnet.
> 
> CNMRI is an imaging facility in Dover, DE, that specializes in neurology
> and sleep medicine. It operates a 1.5-tesla MRI magnet and also performs
> studies such as polysomnography, nerve conduction, and home sleep studies,
> according to Dr. Robert Varipapa, a neurologist at the center.
> 
> In mid-October, field service engineers from an imaging OEM arrived and
> ramped the magnet down and then back up again. Immediately thereafter,
> staff members at the center who owned Apple devices with wireless charging
> reported that their devices were disabled. Approximately eight or nine
> devices were affected, according to Varipapa.
> 
> Only newer-model Apple products such as the iPhone 8 and iPhone 10 were
> affected, he added. Those with older models didn't experience any problems,
> nor did staff with Android phones.
> 
> The Delaware center's experience is similar to that of an Illinois hospital
> that also reported conflict
> s
> between its MRI scanner and iPhones. That site reported that nearly 40
> iPhones stopped working after the installation of a new MRI scanner. The
> problem was attributed to helium gas that may have leaked during the
> installation and found its way into the mechanical workings of the phones.
> 
> But there are also crucial differences between the Illinois incident and
> the experience at the Delaware center. For one thing, the Delaware site
> never experienced a helium leak, to Varipapa's knowledge. Also, while the
> Illinois site reported problems with Apple models at the iPhone 6 level and
> above, in Delaware the problem was restricted to newer models with wireless
> charging -- no iPhone 6 devices were affected, Varipapa told AuntMinnie.com.
> 
> Finally, at the Illinois hospital, some of the iPhones began working again
> after the helium inside the devices apparently dissipated. At CNMRI, all of
> the smartphones were permanently disabled, and staff had to get new ones.
> 
> Varipapa said CNMRI's physicist told him that the center's experience is
> not an uncommon one. The physicist has heard that some field service
> engineers tell staff members to place smartphones in their cars' glove
> boxes when MRI magnets are being serviced, he said.
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Re: [time-nuts] Helium and MEMS oscillators don;t mix well

[Bob kb8tq]

Hi

If you take an IC package up to fairly high pressure for a few hours (and it’s 
defective) you can pretty well fill it with helium and have it well above 1 ATM 
internal 
pressure. It will then leak out (maybe over a few years) until it gets back 
down to one 
atmosphere internally.

 In some really rare conditions, you can pressurize it to high enough PSI to 
inflate the 
package when the pressure goes back to 1ATM. Even then the oscillators 
generally still work ok. 
This is inflation not really a function of helium. It’s just a function of what 
a lot of PSI does to 
a sealed package. You could inflate it with air and see the same thing. 

Getting helium in a properly sealed package  *without* a lot of pressure *and* 
very 
high concentrations (like 100%) …. very difficult. 

Bob

> On Nov 1, 2018, at 3:27 PM, Wayne Holder  wrote:
> 
> The oscillator mentioned in the article is a SiT1532 made by SiTime
> .  It's sold in a chip scale package that's only 1.5mm x
> .9mm, which means it'a no much more than a chip of silicon with some solder
> balls attached.  The data sheet indicates there is a "polymer" coating on
> the back side of the chip, but the working surface would be in the bottom
> where the solder balls are.  There is a rectangular protrusion shown on the
> "Dimensions and Patterns" section (page 12) that's right over where the
> MEMS mechanism would sit that might be some type of seal, but there is no
> descriptive text.
> 
> The curious thing to me is that some iPhones are said not to recover from
> exposure to helium but, as an essentially mechanical device, I can think of
> no reason that the SiT1532 would not recover from exposure to helium after
> the gas had migrated out.  I wonder off the iPhone could be damaged by an
> oscillator failure, o one that's running off frequency? The devices sell
> for about $1.25 at Mouser and I have a tank of helium in the garage, so I'm
> thinking about doing an experiment.  The only problems is finding a way to
> solder wires to such a small part?  Might have to make a PCB, instead.
> 
> Wayne
> 
> On Wed, Oct 31, 2018 at 12:51 PM Mark Sims  wrote:
> 
>> https://ifixit.org/blog/11986/iphones-are-allergic-to-helium/
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Re: [time-nuts] Helium and MEMS oscillators don;t mix well

[Bob kb8tq]

Hi

Now, getting back to the original issue. MEMS oscillators of some types have
really tiny structures in them. They mount them as close to being in “free 
space”
as they can. The idea is no different than a crystal. A properly shape lump 
running 
in free space has higher Q. Higher Q is normally a good thing in an oscillator.

It’s not a great leap to guess that there may be magnetic materials in a 
structure 
like that. If so, a giant magnetic field could put some force on the mounting 
structure.
Put to much force (or to quick a “snap” in that force) and there goes the 
structure into 
really tiny pieces …..

Yes, there are a lot of other EMI possibilities. Last time I checked, things 
like phones 
and watches were not on the list of what you took with you for an MRI ….

Bob

> On Nov 1, 2018, at 3:05 PM, David Witten  wrote:
> 
> Please pardon my usual incompetence posting to mailing lists...
> 
> 2nd MRI center reports problems with Apple devices
> 
> 
> Aunt Minnie is a newsletter/site targeting clinical radiologists and
> technical staff.
> 
> Dave
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Re: [time-nuts] Helium and MEMS oscillators don;t mix well

[David Witten]

Please pardon my usual incompetence posting to mailing lists...

2nd MRI center reports problems with Apple devices


Aunt Minnie is a newsletter/site targeting clinical radiologists and
technical staff.

Dave
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Re: [time-nuts] Helium and MEMS oscillators don;t mix well

[Hal Murray]

kb...@n1k.org said:
> Helium leak testing is a *very* common thing in the oscillator industry. I’d
> bet it also is done in the  MEMS oscillator business as well.

How does that test work?

It seems obvious how to test stuff that is designed to hold Helium - put the 
Helium in and sniff the surrounding air to see if any leaks out.  But how do I 
test a small package to see if any leaks in?

Maybe give it a chance to leak in for a while and then see if any leaks out?


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Re: [time-nuts] Helium and MEMS oscillators don;t mix well

[jimlux]

On 11/1/18 8:52 AM, Poul-Henning Kamp wrote:


In message , Bob kb8tq writes:


A lot of Radon and *really* poor ventilation….


Yup.

But a LOT of Radon is not without interesting "side-effects", such as
much easier ionization due to the alpha radiation.

To get to relevant He levels via the Radon route, we are talking
deep unventilated mineshaft kind of concentrations...

Hydrogen is a lot more plausible in my view.




Yeah, but in concentrations typical in the "room", I doubt you'd see the 
effect.  The experimenters put the phone in a bag full of helium and it 
took hours.  I would expect the same in hydrogen.


That's a lot different than a <1% concentration. I assure you, that if 
there was a helium leak/vent/boil off that made the room concentration 
1%, the room oxygen sensor would be alarming (having dropped to 20%) and 
people would be running for the doors.


I'd be betting more on some RFI/EMI issue from the RF fields or the 
magnetic fields, both of which are quite strong in an MRI facility.




However, in true time-nuts fashion, I'm going to rummage around for some 
older SiTime oscillators on an eval board at work, and we can do a 
*real* test.


I got some samples from them a few years ago, so all I have to do is 
find that tiny plastic bag with the tiny 2x2mm parts in it.


Then I have to find some spare hydrogen and helium..

After all, we really need to evaluate it in an atmosphere of Argon and 
CO2,  (Mars gas) - I'll see if we've got some around - we were doing RF 
breakdown tests in simulated Martian atmosphere   (BTW, the 
Martian atmosphere is unique in that it probably has the lowest "minimum 
sparking voltage" in the universe)








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Re: [time-nuts] Helium and MEMS oscillators don;t mix well

[Poul-Henning Kamp]

In message , Bob kb8tq writes:

> A lot of Radon and *really* poor ventilation…. 

Yup.

But a LOT of Radon is not without interesting "side-effects", such as
much easier ionization due to the alpha radiation.

To get to relevant He levels via the Radon route, we are talking
deep unventilated mineshaft kind of concentrations...

Hydrogen is a lot more plausible in my view.


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Re: [time-nuts] Helium and MEMS oscillators don;t mix well

[Bob kb8tq]

Hi

A lot of Radon and *really* poor ventilation…. 

There are a lot of ways for He to show up. In normal use, issue is hanging on 
to it. 
It tends to run away from its source very quickly. Maintaining a measurable 
concentration 
in something like a normal room …. not very easy at all. 

Bob

> On Nov 1, 2018, at 3:04 AM, Poul-Henning Kamp  wrote:
> 
> 
> In message , "Richard 
> (Rick
> ) Karlquist" writes:
> 
>> According to Jack, radon emits alpha particles, AKA helium nuclei.
>> These capture stray electrons and become helium atoms.  So the
>> presence of helium is a marker for radon.  The fact that the half
>> life is a few days supports this hypothesis.   At least that is what
>> Jack told me.
> 
> Right, but you need a LOT of Radon before the Helium concentration
> becomes a problem, and the alphas would literally make things
> glow in the dark.
> 
> -- 
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
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> Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] Helium and MEMS oscillators don;t mix well

[Poul-Henning Kamp]

In message , "Richard (Rick
) Karlquist" writes:

>According to Jack, radon emits alpha particles, AKA helium nuclei.
>These capture stray electrons and become helium atoms.  So the
>presence of helium is a marker for radon.  The fact that the half
>life is a few days supports this hypothesis.   At least that is what
>Jack told me.

Right, but you need a LOT of Radon before the Helium concentration
becomes a problem, and the alphas would literally make things
glow in the dark.

-- 
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Re: [time-nuts] Helium and MEMS oscillators don;t mix well

[Richard (Rick) Karlquist]

This reminds me of a Jack Kusters (of HP fame) anecdote.
He left HP for a while to work for Ephratom on Rb standards.
Some customer was raising hell about their Ephratom Rb
standards having lousy accuracy.  Jack had them send
some of the "defective" units back to the factory, and
the units were indeed having accuracy problems at first,
but eventually returned to the good accuracy they had
when they left the factory.  Jack decided that the
explanation must be helium.  Jack tried to diplomatically
ask the customer if they used helium in their facility.
They said no and accused Jack of using helium as an
red herring to cover up their lousy product.  Jack then
asked again that we wanted to make sure they don't use
helium in their plant.  They again emphatically denied
any use of helium.  At which point Jack pointed out
that in that case, it was clear than they had a radon
incursion in their facility.  And he made them a deal:
if they would stop submitting warranty claims, he would
refrain from publicizing their radon situation.  That
took care of the problem.

Rick

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Re: [time-nuts] Helium and MEMS oscillators don;t mix well

[Jeremy Elson]

I just came here to post that same link. Very interesting bit of hardware
detective work.


On Wed, Oct 31, 2018 at 12:51 PM Mark Sims  wrote:

> https://ifixit.org/blog/11986/iphones-are-allergic-to-helium/
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